The present invention relates to an AWG (arrayed waveguide grating) that is applied to an optical communication device and used in multiplexing/demultiplexing communication lights of different wavelength, and the present invention relates to an optical multiplex/demultiplex system and an optical multiplexer/demultiplexer using the AWG.
The AWG is a waveguide diffraction grating which utilizes the phase difference made by the difference of optical path length between arrayed waveguides. In the following, the principle of the AWG will be explained in comparison with a prior art.
In the conventional diffraction grating type demultiplexer, incident lights of different wavelength inputted to a diffraction grating from an input optical fiber are separated into the respective wavelength by the angles. Then, the angles of the wavelengths are converted into variations of positions by an optical lens and converged to an output optical fiber. In this way, in the prior art diffraction grating, a wavelength dispersion has been realized by an interference effect created by the phase difference owing to the periodic structure of the grating.
On the other hand, in the AWG of the present invention, a plurality of channel waveguides are provided with a fixed deviation of the optical path length, and an interference effect created at the output ends realizes segmentation of the lights according to the angle of the respective wavelengths. As the optical element which is equivalent to the optical lens of the prior art diffraction grating type demultiplexer, in the AWG of the present invention, a fan-shape slab waveguide is used, in which a plurality of channel waveguides are positioned in an arc shape.
In the above-mentioned fan-shape slab waveguide, arrayed input/output waveguide groups and an arrayed waveguide group are positioned in an arc shape, keeping a fixed distance from each other. The curvature center of the fan-shape slab waveguide is positioned at an arrayed input/output waveguide group, and an arrayed waveguide is positioned in a radial pattern so that the optical axis goes through the curvature center. Since there is no horizontal optical confinement in a slab waveguide, lights outputted from one input waveguide are spread out in a radial pattern by diffraction, and an arrayed waveguide group of the AWG is driven at the same phase. The arrayed waveguide group of the AWG is composed of a plurality of channel waveguides which are separated from each other having a difference (xcex94L) in length. The difference (xcex94L) in length causes a constant amount of phase shift at the output ends of the arrayed waveguides, and the interference effect created by the phase shift brings about a dispersion of the wavelength.
FIG. 1 is a plane view showing a construction of a prior art AWG. Referring to FIG. 1, the principle of the AWG will be explained taking a demultiplexing operation as an example. In FIG. 1, the conventional AWG comprises an input waveguide 121, an input-side slab waveguide 122, an arrayed waveguide group 123, an output-side slab waveguide 124, an output waveguide 125 on a waveguide substrate 120. An input fiber array 126 is connected to the input waveguide 121, and an output fiber array 127 to the output waveguide 125.
Multiplexed lights xcex1 to xcexn go through a single fiber 128 and the input fiber array 126, and are made incident into the input waveguide 121. The multiplexed lights xcex1 to xcexn are spread in a radial pattern by the input-side slab waveguide 122 and segmented to the arrayed waveguide group 123 at the same phase at almost the same photon quantities. The arrayed waveguide group 123 is composed of a plurality of waveguides, and each of them has a difference (xcex94L) in length. When the multiplexed lights xcex1 to xcexn propagate through the arrayed waveguide group 123, the optical phase difference is created. Undergoing a multiple beam diffraction interference at the output-side slab waveguide 124, the multiplexed lights xcex1 to xcexn are converged at the output waveguide 125 corresponding to each wavelength, and thus demultiplex is realized. The demultiplexed lights xcex1 to xcexn outputted to each of the output waveguides 125 go through the output fiber array 127 and are outputted to a tape fiber 129. The demultiplexed lights xcex1 to xcexn have a wavelength profile with a center wavelength which causes loss at a minimum level.
One of the prominent characters of the AWG is to be able to design the specific character freely by such as making appropriate selection of the length of arrayed waveguides or the space between them. Up to this point, a variety of multiplexers/demultiplexers with the AWG have been realized by utilizing such materials as a siliceous material, a semiconductor and a polymer.
FIG. 2 is a sectional view of a module structure provided with the conventional AWG. In FIG. 2, a module 130 includes at the lower layer within a case 131, a temperature controlling device (i.e., a peltier device) 132, an AWG element 133, a temperature detecting device (i.e., a thermistor device) 134, an input fiber array 135, an output fiber array 136 (fiber arrays 135 and 136 are positioned at both ends of the AWG element), a single fiber 137 and a tape fiber 138, and at the upper part a cover 139. According to the module structure shown in FIG. 2, the single fiber 137 and the tape fiber 138 are extended from the both ends of the module comprising the case 131 and the cover 139.
Recently, in optical communication network, an optical communication device has come into use for network nodes which perform not only simple point-to-point transmission, but also circuit switching and input/output of signals. Thus, the optical communication device for structuring a network with larger capacity, higher flexibility and reliability has become essential.
In particular, a demand for the AWG as an optical communication device of the sort is rapidly increased in accordance with multiplexing and increase in the number of wavelength in the optical communication system. Consequently, it is urgently required to have a miniaturized AWG with the lower price.
However, the above-mentioned conventional AWG has some problems as follows. First of all, since an element is enlarged due to increase in the number of wavelengths, quantity of elements which can be obtained from one wafer is decreased. Secondly, since characteristic dispersion occurs due to increase in the number of wavelengths, non-defective ratio is lowered, that is a yielding percentage (non-defective products/gross product) is deteriorated. Thirdly, since an optical communication system has become highly efficient and the AWG has been required to have high specifications, it is hard to secure a non-defective AWG. Furthermore, as is apparent from the above-mentioned structure of a module, since a single fiber and a tape fiber are extended from the both ends of the module, there are increase in the mounting area and a limitation in the mounting position.
Accordingly, it is an object of the present invention to provide an AWG, an optical multiplex/demultiplex system and an optical multiplexer/demultiplexer with the AWG, which realize miniaturization and lowering the price, as well as, have less limitation in the mounting space and position.
In other words, the present invention provides an AWG, an optical multiplex/demultiplex system and an optical multiplexer/demultiplexer with the AWG, which realize miniaturization and lowering the price, by composing a plurality of selective circuits within one element, and converging input/output waveguides of both multiplex side and demultiplex side at given one side of the element.
In order to achieve the above object, an AWG in accordance with the first aspect of the present invention is structured by forming multiple waveguides on a substrate, and has a plurality of selective circuits.
In accordance with the second aspect of the present invention, in the first aspect, input ends and output ends of each of the multiple circuits are disposed on an arbitrary side of a substrate.
In accordance with the third aspect of the present invention, in the second aspect, the input ends and output ends are adjacently disposed at one side of the substrate.
In accordance with the fourth aspect of the present invention, in the second or the third aspect, the input ends and output ends of each of the multiple circuits are disposed at any two sides of the substrate respectively.
In accordance with the fifth aspect of the present invention, in the fourth aspect, the input ends and output ends of each of the multiple circuits are disposed at any two opposite sides of the substrate respectively.
In accordance with the sixth aspect of the present invention, in the fourth aspect, the input ends and output ends of each of the multiple circuits are disposed at any two adjacent sides of the substrate respectively.
In accordance with the seventh aspect of the present invention, in one of the aspects first to sixth, the AWG selects and uses one of the multiple circuits.
In accordance with the eighth aspect of the present invention, in one of the aspects first to seventh, a plurality of the circuits are composed of a first circuit and a second circuit.
In accordance with the ninth aspect of the present invention, in the eighth aspect, the first circuit comprises first input/output waveguides at multiplex side, a first slab waveguide at multiplex side, second input/output waveguides at demultiplex side, a second slab waveguide at demultiplex side and a first arrayed waveguide group connecting the first slab waveguide and the second slab waveguide.
In accordance with the tenth aspect of the present invention, in the eighth aspect or the ninth aspect, the second circuit comprises third input/output waveguides at multiplex side, a third slab waveguide at multiplex side, fourth input/output waveguides at demultiplex side, a fourth slab waveguide at demultiplex side and a second arrayed waveguide group connecting the third slab waveguide and the fourth slab waveguide.
In accordance with the eleventh aspect of the present invention, in the tenth aspect, on the substrate the first slab waveguide and the third slab waveguide are intersected, and the second slab waveguide and the fourth slab waveguide are intersected.
In accordance with the twelfth aspect of the present invention, in the eleventh aspect, the cross-point of the first slab waveguide and the third slab waveguide and the cross-point of the second slab waveguide and the fourth slab waveguide are positioned on the substrate, wherein the two cross-points form a line symmetry whose axis is the line segment combining the center points of the first arrayed waveguide group and the second arrayed waveguide group.
In accordance with the thirteenth aspect of the present invention, in one of the aspects tenth to twelfth, the ends of the first input/output waveguides and the second input/output waveguides and the ends of the third input/output waveguides and the fourth input/output waveguides are positioned at an arbitrary side of the substrate.
In accordance with the fourteenth aspect of the present invention, in the thirteenth aspect, the ends of the first input/output waveguides and the second input/output waveguides and the ends of the third input/output waveguides and the fourth input/output waveguides are adjacently positioned at an arbitrary side of the substrate respectively.
In accordance with the fifteenth aspect f the present invention, in one of the aspects tenth to fourteenth, the ends of the first input/output waveguides and the second input/output waveguides and the ends of the third input/output waveguides and the fourth input/output waveguides are positioned at any two sides of the substrate respectively.
In accordance with the sixteenth aspect of the present invention, in one of the aspects tenth to fifteenth, the ends of the first input/output waveguides and the second input/output waveguides and the ends of the third input/output waveguides and the fourth input/output waveguides are positioned at any two opposite sides of the substrate respectively.
In accordance with the seventeenth aspect of the present invention, in one of the aspects tenth to fifteenth, the ends of the first input/output waveguides and the second input/output waveguides and the ends of the third input/output waveguides and the fourth input/output waveguides are positioned at any two adjacent sides of the substrate respectively.
In accordance with the eighteenth aspect of the present invention, in one of the aspects first to seventh, a plurality of the circuits are composed of a first circuit, a second circuit, a third circuit and a fourth circuit.
In accordance with the nineteenth aspect of the present invention, in the eighteenth aspect, the first circuit comprises first input/output waveguides at multiplex side, a first slab waveguide at multiplex side, second input/output waveguides at demultiplex side, a second slab waveguide at demultiplex side and a first arrayed waveguide group connecting the first slab waveguide and the second slab waveguide.
In accordance with the twentieth aspect of the present invention, in the eighteenth or the nineteenth aspect, the second circuit comprises third input/output waveguides at multiplex side, a third slab waveguide at multiplex side, fourth input/output waveguides at demultiplex side, a fourth slab waveguide at demultiplex side and a second arrayed waveguide group connecting the third slab waveguide and the fourth slab waveguide.
In accordance with the twenty-first aspect of the present invention, in one of the aspects eighteenth to twentieth, the third circuit comprises fifth input/output waveguides at multiplex side, a fifth slab waveguide at multiplex side, sixth input/output waveguides at demultiplex side, a sixth slab waveguide at demultiplex side and a third arrayed waveguide group connecting the fifth slab waveguide and the sixth slab waveguide.
In accordance with the twenty-second aspect of the present invention, in one of the aspects eighteenth to twenty-first, the fourth circuit comprises seventh input/output waveguides at multiplex side, a seventh slab waveguide at multiplex side, eighth input/output waveguides at demultiplex side, a eighth slab waveguide at demultiplex side and a fourth arrayed waveguide group connecting the seventh slab waveguide and the eighth slab waveguide.
In accordance with the twenty-third aspect of the present invention, in the twenty-second aspect, on the substrate the first slab waveguide, the third slab waveguide, the fifth slab waveguide and the seventh slab waveguide are intersected, and the second slab waveguide, the fourth slab waveguide, the sixth slab waveguide and the eighth slab waveguide are intersected.
In accordance with the twenty-fourth aspect of the present invention, in the twenty-third aspect, the cross-point of the first slab waveguide, the third slab waveguide, the fifth slab waveguide and the seventh slab waveguide and the cross-point of the second slab waveguide, the fourth slab waveguide, the sixth slab waveguide and the eighth slab waveguide are positioned on the substrate, and the two cross-points form a line symmetry whose axis is the line segment combining the respective center points of the first arrayed waveguide group, the second arrayed waveguide group, the third arrayed waveguide group and the fourth arrayed waveguide group.
In accordance with the twenty-fifth aspect of the present invention, in one of the aspects twenty-second to twenty-fourth, the ends of the first input/output waveguides and the second input/output waveguides, the ends of the third input/output waveguides and the fourth input/output waveguides, the ends of the fifth input/output waveguides and the sixth input/output waveguides and the ends of the seventh input/output waveguides and the eighth input/output waveguides are positioned at an arbitrary side of the substrate respectively.
In accordance with the twenty-sixth aspect of the present invention, in the twenty-fifth aspect, the ends of the first input/output waveguides and the second input/output waveguides, the ends of the third input/output waveguides and the fourth input/output waveguides, the ends of the fifth input/output waveguides and the sixth input/output waveguides and the ends of the seventh input/output waveguides and the eighth input/output waveguides are adjacently positioned at an arbitrary side of the substrate respectively.
In accordance with the twenty-seventh aspect of the present invention, in one of the aspects twenty-second to twenty-sixth, the ends of the first input/output waveguides and the second input/output waveguides, the ends of the third input/output waveguides and the fourth input/output waveguides, the ends of the fifth input/output waveguides and the sixth input/output waveguides and the ends of the seventh input/output waveguides and the eighth input/output waveguides are positioned at any two sides of the substrate respectively.
In accordance with the twenty-eighth aspect of the present invention, in one of the aspects twenty-second to twenty-seventh, the ends of the first input/output waveguides and the second input/output waveguides, the ends of the third input/output waveguides and the fourth input/output waveguides, the ends of the fifth input/output waveguides and the sixth input/output waveguides and the ends of the seventh input/output waveguides and the eighth input/output waveguides are positioned at any two opposite sides of the substrate respectively.
In accordance with the twenty-ninth aspect of the present invention, in one of the aspects twenty-second to twenty-seventh, the ends of the first input/output waveguides and the second input/output waveguides, the ends of the third input/output waveguides and the fourth input/output waveguides, the ends of the fifth input/output waveguides and the sixth input/output waveguides and the ends of the seventh input/output waveguides and the eighth input/output waveguides are positioned at any two adjacent sides of the substrate respectively.
In accordance with the thirtieth aspect of the present invention, there is provided an optical communication system constructed with the AWG in one of the aspects first to twenty-ninth.
In accordance with the thirty-first aspect of the present invention, there is provided an optical multiplexer/demultiplexer constructed with the AWG in one of the aspects first to twenty-ninth.
The present invention relates to the AWG which is applied to an optical network node in an optical communication system, comprising a plurality of selective circuits as a device which multiplexes or demultiplexes communication lights with different wavelengths. In the AWG, the core end faces of input ends and output ends of the circuits are converged at an arbitrary side of a substrate.